A perennial problem in the mass spectrometric analysis of both biological and environmental samples is that the absolute level of analyte is extremely low. One approach to this problem is to develop low volume-high flux delivery systems for the mass spectrometer. We have undertaken the development of interfaces for nanoliter capillary systems and MS. These capillary systems offer the same advantages over wider-bore LC systems that capillary GC offers over packed-column GC, a high flux of analyte into the MS but with a significantly lower total analyte level necessary. Current developments are in the areas of continuous flow FAB (CF-FAB), and capillary zone electrophoresis (CZE). In the area of CF-FAB we have developed packed (50-75 mu id) columns for use in the analysis of peptide and protein digests. The greater loading capacity of these columns provides a higher dynamic range than do OTLC columns and is, thus, more suitable for complex mixtures and low level analyses. These column are also very compatible with MS/MS data acquisition. In the area of CZE we have successfully interface CZE with both CF-FAB and electrospray ionization. Both techniques have been found suitable for the determination of peptides and protein digests in the femtomolar concentration range. In conjunction with ESI and mass spectral data, proteins with MR 2> 30,000 can be separated and their mass spectra obtained.